Dual port thermodilution catheter

ABSTRACT

A catheter for monitoring heart function comprises a catheter tube having a plurality of lumens. The catheter includes an inflatable balloon at a distal tip of the catheter tube for positioning the catheter in a wedged position within a pulmonary artery within the heart of a patient. Dual injectate ports are formed in a side wall of the catheter tube. Each port communicates with a respective injectate lumen carried in the catheter tube. When inserted into the heart of a patient, either the first or second injectate port is positioned within the desired distance from the tricuspid valve for thermodilution depending upon the size of the heart. Thermodilution to obtain cardiac output and/or right heart ejection fraction is implemented by injecting injectate through the lumen associated with the port properly positioned relative the tricuspid valve and discharged through the corresponding port.

FIELD OF THE INVENTION

The present invention relates to catheters, and, in particular, tocatheters which utilize thermodilution techniques to measure cardiacoutput.

BACKGROUND OF THE INVENTION

Multiple lumen catheters are commonly used to measure and monitorcardiac output. In operation, the catheter is typically introduced intoa central vein of a patient and advanced toward the right atrium throughthe superior or inferior vena cava. Once the distal tip of the catheteris positioned within the vena cava, a small balloon positioned over thedistal tip is inflated through an inflation lumen provided in thecatheter. The balloon carries the catheter along the flow of bloodthrough the right atrium and right ventricle into the main pulmonaryartery. The catheter continues to advance until a wedge position isreached within an individual pulmonary artery wherein the balloon sealsoff the inflow of blood through the artery. In this position, pulmonaryartery wedge pressure measurements are commonly taken and the balloonthen deflated.

Subsequent to balloon deflation, thermodilution techniques arefrequently utilized to measure cardiac output. Using thermodilution, abolus of cold saline injectate is injected through a port incommunication with one lumen of the catheter into the blood stream, andthe resulting temperature change is measured with a thermistor locatedat a distal end of the catheter. Right heart ejection fraction can alsobe measured with thermodilution techniques in a known manner by furthermonitoring the occurrence of contractions using electrodes which arepositioned at the distal end of the catheter within the right ventricle.

To achieve optimum accuracy using thermodilution techniques, theinjectate is injected into the right atrium in an abrupt manner so as tobe evenly distributed and well mixed in the right ventricle prior toejection through the pulmonary artery. Commonly, the injectate isinjected through a port located approximately 5 cm proximal of thetricuspid valve, adjacent the right atrium. When injected in thismanner, the injectate flows countercurrent to the blood flow from theinferior vena cava, and thorough mixing with the incoming blood isachieved. Often, the injectate port comprises plural openings to furtherassist in injectate mixing and distribution within the blood stream.

Because heart size varies from patient to patient, the location of theinjectate port once the distal tip of the catheter is positioned withinthe individual pulmonary artery also varies. Often, the catheter must bemanually repositioned prior to thermodilution in order to locate theinjectate port at the desired distance from the tricuspid valve. Then,once the thermodilution process has been completed, the catheter must berepositioned at the desired location within the pulmonary artery. Thisrepositioning increases the risk of infection, the risk of damage to theheart and pulmonary artery caused by wall perforation, and furtherincreases the amount of time that must be spent by the attendingphysician to perform the desired procedures.

SUMMARY OF THE INVENTION

The present invention provides a cardiac output catheter having dualinjectate ports. The catheter comprises a flexible catheter tube havinga proximal and a distal end. The catheter tube includes a plurality oflumens including two injectate lumens which are in communication withthe two injectate ports. An inflatable balloon located at the distal endof the catheter carries the catheter to a wedged position within apulmonary artery when the catheter is inserted into the heart of apatient. Depending upon the size of the heart, either the first orsecond injectate port is positioned within the desired distance proximalthe tricuspid valve for thermodilution, preferably within 2-5 cm of thevalve. Thermodilution techniques to obtain cardiac output and/or rightheart ejection fraction data are implemented by injecting a bolus ofcold saline injectate through the lumen in communication with theinjectate port properly positioned relative the tricuspid valve. Theinjectate is mixed with the blood flow in the right atrium and flowsthrough the pulmonary artery past a thermistor at the distal end of thecatheter which transmits data to appropriate electronic devices formeasuring cardiac output and/or right heart ejection fraction.

In accordance with the present invention, a catheter for use inmonitoring heart function is disclosed wherein the catheter comprises aninflatable balloon for positioning a distal end of the catheter in apulmonary artery. The catheter additionally comprises plural lumens andcorresponding plural injectate ports for injecting fluid proximal to thetricuspid valve of the heart, a first of said injectate ports beinglocated closer to said balloon than a second of said injectate ports.The plural injectate ports are spaced to accommodate hearts of differentsizes, whereby one of the injectate ports is positioned proximal to thetricuspid valve when said balloon is in said pulmonary artery. Each ofthe injectate ports may comprise an array of closely spaced openings.

The present invention further provides a method of using athermodilution catheter comprising inserting the thermodilution catheterinto the heart of a patient, positioning one of plural injectate portsin the catheter proximal to the tricuspid valve of the heart,positioning another of the plural injectate ports further away from thetricuspid valve than the one injectate port, and injecting fluid throughthe one of the plural injectate ports. The method may additionallycomprise the subsequent steps of detecting an unintended change inposition of the one injectate port relative to the tricuspid valve, andutilizing another of said injectate ports to inject the fluid.

In a further aspect of the invention, a method of manufacturing athermodilution catheter having plural lumens and an inflatable balloonfor positioning a distal end of the catheter in a pulmonary artery isdisclosed comprising forming openings in a wall of said catheter toprovide plural injectate ports for receiving fluid from plural lumens,respectively, and locating the injectate ports to accommodate hearts ofdifferent sizes such that one of the injectate ports is proximal to thetricuspid valve for a relatively large heart and another of theinjectate ports is proximal to the tricuspid valve for a relativelysmall heart. In large hearts, the injectate port located in the rightventricle can be used for right ventricle (RV) pressure recordingsimultaneously to right ventricle ejection fraction (RVEF) measurementallowing definition of pressure volume points defining systolic anddiastolic RV function. The dual port design augments visibility ofcatheter migration, and thus increases safety, by dual port pressuremonitoring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cardiac output catheter in accordancewith the present invention;

FIG. 2 is a cross-sectional view of the catheter taken along lines 2--2of FIG. 1;

FIG. 3 illustrates the catheter in a wedged position when inserted intoa relatively small heart;

FIG. 4 illustrates the catheter in a wedged position when inserted intoa relatively large heart;

FIG. 5 illustrates the position of the injectate ports in the smallheart when forward movement of the catheter occurs.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a cardiac output catheter 10 for monitoring heartfunction in accordance with the present invention. The cathetercomprises a flexible catheter tube 12 extruded from a biocompatibleplastic material such as radiopaque polyvinylchloride. As shown in FIG.2, the catheter tube 12 comprises a plurality of lumens, including afirst smaller, circular lumen 14 for balloon inflation; a second smallercircular lumen 18 which carries thermistor and electrode wires; asubstantially rectangular fiber optic lumen 20; a first larger,generally circular lumen 16 for infusion and for carrying electrodewires; a second larger, generally circular distal through lumen 22; athird larger, generally circular lumen 26 for infusion and injectate;and a generally kidney-shaped injectate lumen 28.

Referring to FIG. 1, a balloon inflation tube 30, an infusion tube 32,and a distal lumen tube 34 are fused to the catheter tubing 12 withinthe balloon inflation lumen 14, infusion lumen 16, and distal throughlumen 22, respectively. Further, first and second injectate tubes 36, 38are fused to the catheter tube 12 within the first and second injectatelumens 24, 26. A first insulating tube 40 is fused to the catheter tube12 within the lumen 18 which carries the thermistor and electrode wires.The wires are separated in a connector 42 which couples the wires toindividual conduits 44 having couplers 46, 48, 50 which can be attachedto conventional electronic monitoring devices. A second insulating tube52 is fused to the fiber optic lumen 20 and includes a connecter 54 forcoupling the tube 52 and optical fiber carried therein to suitablemonitoring equipment. A sleeve 56 covers the tubes 30, 32, 34, 36, 38,40, 52 at their attachment to the catheter tube 12.

The catheter tube 12 comprises a proximal end 60, a portion of which isenclosed within the sleeve 56, and a distal end 62 opposite the proximalend 60. A port 64 at the distal tip communicates with the distal throughlumen 22 and provides a means by which pressures within the body may bemonitored. The distal end 62 of the catheter tube 12 further includes aballoon inflation port 66 which communicates with the balloon inflationlumen 14. An inflatable balloon 68 is located at the distal end 62 ofthe catheter 10, adjacent the balloon inflation port 66. A thermistor(not shown) is positioned inside the lumen 18 carrying thermistor andelectrode wires and is mounted in accordance with the manner describedin U.S. Pat. No. 4,407,304 entitled "Method of Mounting an ElectricalLead in a Catheter Body" and assigned to the assignee of the presentinvention. The thermistor is exposed through an opening 70 in the distalend 62 of the catheter 10. The thermistor leads extend through thelength of the lumen 18 to the connector 42. The lumen 18 further carriesleads attached to electrodes 72, 74, located at the proximal and distalends 60, 62, respectively, of the catheter tube used in measuring rightheart ejection fraction.

A first injectate port 80 is formed in a side wall of the catheter 10 incommunication with the first injectate lumen 24. A second injectate port82 is formed in the side wall of the catheter 10, proximate the firstinjectate port 80, in communication with the second injectate lumen 26.As shown, the first injectate port 80 is located closer to theinflatable balloon 68 than the second injectate port 82. It is desirablethat the injectate ports 80, 82 are spaced from each other by about15-20% of the distance between the first injectate port 80 and theballoon 68. In the preferred embodiment, the injectate ports 80, 82 arespaced apart by approximately 3-4 cm for superior vena cava insertion,such that the first injectate port 80 is located approximately 19 to 21cm from the balloon 68, and the second injectate port 82 is locatedapproximately 22 to 25 cm from the balloon 68. For inferior vena cavainsertion, the spacing between the injectate ports 80, 82 is larger andcan be up to 7 cm. The first and second injectate ports 80, 82preferably comprise a plurality or array of closely spaced openingsformed in the side wall of the catheter 10. In the preferred embodiment,each port comprises three round openings 90 (FIGS. 3-5). The openings 90are offset from each other so that they follow a slightly arcuate pathin the side wall of the catheter tube 12, and thereby reduce thepossibility of stress induced tears between the openings 90.

As illustrated in FIG. 3 and FIG. 4, the catheter 10 is inserted into aheart 100 through the superior vena cava 102 and into the right atrium104. Alternatively, the catheter 10 may be inserted into the rightatrium 104 through the inferior vena cava 106. Once within the rightatrium 104, the balloon 68 is inflated with air or CO₂ exiting throughthe inflation port 66 adjacent the distal tip to inflate the balloon 68,which then carries the catheter 10 with the bloodstream through theright ventricle 108 and into the main pulmonary artery 110. Inside themain pulmonary artery 110, the catheter 10 is advanced until the balloon68 reaches a wedged position within an individual pulmonary artery 112.In this position, pulmonary artery wedge pressure measurements may betaken at the distal port 64 in accordance with conventional pressuremonitoring techniques. After the desired wedge pressure measurementshave been obtained, the balloon 68 is then deflated.

When inserted as described above into a patient having a small heart100, illustrated in FIG. 3, the first injectate port 80 is positioned inthe right atrium 104, approximately within 2-5 cm proximate thetricuspid valve 120, while the second injectate port 82 is locatedfarther back in the right atrium 104 as shown. Once the balloon 68 hasbeen deflated, conventional thermodilution techniques may be implementedto obtain measurements and data from which cardiac output and rightheart ejection fraction can be determined. To determine cardiac outputand/or right heart ejection fraction utilizing thermodilutiontechniques, cold saline injectate is injected into the heart through thefirst injectable lumen 24 and discharged through the plural openings 90comprising the first injectate port 80. The plural openings 90 allow theinjectate to become well mixed with the countercurrent blood flow fromthe inferior vena cava 106 prior to entering the right ventricle 108.The blood flow from the superior vena cava 102 holds the mixture in theright atrium 104 above the tricuspid valve 120, such that when the valve120 is opened, substantially all the mixture is discharged into theright ventricle 108 and travels through the pulmonary artery 110 pastthe thermistor. In accordance with well-known techniques, temperatureinformation obtained by the thermistor is transmitted through the leadscontained in the first insulation tube 40 and to suitable monitoringdevices via the coupler 50.

As illustrated in FIG. 4, if the catheter 10 is inserted in a patienthaving a larger size heart 200, a greater portion of the length of thecatheter 10 will need to be inserted in order to locate the balloon 68in a wedged position within the pulmonary artery 110. In the largerheart 200, the second injectate port 82 is then positioned within thedesired 2-5 cm proximal the tricuspid valve 120. In this position, thefirst injectate port 80 will typically be located substantially in theright ventricle 108, and thus this port 80 will not be properly locatedfor thermodilution purposes. Accordingly, for large hearts,thermodilution to obtain cardiac output or right heart ejection fractionmeasurements is implemented using the second injectate port 82. A coldsaline injectate is injected through the second injectate lumen 26 anddischarged through the openings 90 comprising the second injectate port82. The injectate mixes with the blood flow and travels through theheart 200 past the thermistor located at the distal end 62 of thecatheter tube 12 in the pulmonary artery 110. As previously described,the thermistor transmits temperature information through the coupler 50to suitable monitoring devices from which cardiac output and/or rightheart ejection fraction can be determined. The first injectate port 80located in the right ventricle 108 gives RV pressure volume relationsfor systolic and diastolic RV function definition simultaneously toright ventricle ejection fraction measurement.

With the dual injection ports 80, 82 of the present invention, thedifficulties associated with manual positioning of a single injectateport relative the tricuspid valve 120 are virtually eliminated. Due tothe ease of positioning the catheter of the present invention, valuablephysician time is decreased and risks associated with moving thecatheter, such as wall perforation are significantly decreased.

Occasionally, forward migration of the catheter 10 can occur after theballoon 68 is deflated. Such migration, due, e.g., to the pulsatingaction of the heart, can cause an unintended change in position of theinjectate ports 80, 82 relative to the tricuspid valve 120. FIG. 5illustrates catheter position within the small heart 100 when movementof the catheter 10 within the heart 100 after balloon deflation occurs.In this situation, the first injectate port 80 is no longer located inthe optimum position relative the tricuspid valve 120, i.e., the firstport 80 will be shifted to a location in the right ventricle. Such acondition can be readily detected by monitoring the pressuremeasurements taken at the injectate ports to determine a shift in portlocation from the position in the right atrium 104 to a position in theright ventricle 108. With the dual port design of the present invention,this migration in the small heart will then bring the second port 82into a position proximal the valve 120, and thermodilution can beimplemented by injecting fluid through the second injectate lumen 26 tobe discharged through the second injectate port 82, thereby savingphysician time and reducing the risks associated with majorrepositioning of the catheter.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described embodimentsare to considered in all respects only as illustrative and notrestrictive. The scope of the invention is, therefore, indicated by theappended claims rather than by the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto embraced within their scope.

What is claimed is:
 1. A method of using a thermodilution catheter having a plurality of injectate ports comprising:a. inserting said thermodilution catheter into the heart of a patient; b. positioning at least a first of said plural injectate ports in said catheter proximal to the tricuspid valve of the heart; c. positioning at least a second of said plural injectate ports upstream from said first injectate port with respect to the direction of blood flow; d. discharging fluid through only said first injectate port.
 2. The method of claim 1, additionally comprising:subsequent to steps (a), (b), (c) and (d), detecting a change in position of said first injectate port relative to said tricuspid valve; and discharging fluid through only said second injectate port.
 3. The method of claim 2, wherein said change in position is caused by action of the patient's heart on the catheter.
 4. The method of claim 2, wherein said change in position is determined by monitoring pressure to detect a shift of said first injectate port from the right atrium of the heart to the right ventricle of the heart. 